Means for use in examining the contours of gear wheel teeth



4 Sheets-Sheet l f Ellilllll/l IIT J. W. SNARRY Filed NOV. 3, 1952 MEANS'FOR USE IN EXAMINING THE CONTOURS OF GEAR WHEEL TEETH Sept . (NYQNTOKSept. 3,` 1935. J; w. sNARRY MEANS FOR USE IN EXAMINING THE CONTOURS OFGEAR WHEEL TEETH Filed Nov. 3, 1932 4 sheets-sheet 24 J mim Sept. 3,1935. J. w. sNARRY MEANS FOR USE IN EXAMINING- THE CONTOURS OF' GEARWHEEL TEETH Filed Nov. 5, 1932 4 Sheets-Sheet 5 Muff/vnf?l JMSnangglill- J. W. SNARRY MEANS FOR USE 1N EXAMINING THE coNToURs oF GEAR WHEELTEETH Sept. 3, 1935.

, 1932 4 SheeS-Shee'cl 4 Filed Nov. 5

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Patented Sept. 3, 1935 MEANS FR USE IN EXAMINENG THE CONTURS F GEARWHEEL TEETH Application November 3, 1932, Serial No. 641,095 in GreatBritain November 30, i931 2 Claims.

This invention has for its object to provide improved means for use inexamining the contours of gear wheel teeth, and particularly fordetermining the presence cf errors in such teeth.

The invention comprises the combination of a iixed body having acircular portion, means for securing the workpiece coaxially with thesaid body, a member rotatable about the axis of the xed body, a feelerslidably mounted on the rotatable member and adapted to move in contactwith the gear tooth to be examined, a tensioned flexible memberembracing a part of the circular portion of the fixed body, and meansfor interconnecting the rotatable member, the ieeler and the flexiblemember, the arrangement being such that inaccuracy of tooth form willcause therfeeler to move relatively to the rotatable member, and suchmovement is indicated by a suitable measuring or indicating instrument.

In the four accompanying sheets of explanatory drawings,

Figures 1 and 2 are respectively a plan and an end View of a contourtesting machine embodying the invention, whilst Figures 3 and 4 arerespectively an elevation and another plan view of the machine showingoperating mechanism not shown in Figures l and 2, but omitting some ofthe parts shown in these latter gures.

Referring to the drawings, I employ a body a having a circular portionof any suitable diameter which is larger than the diameter of the basecircle b or pitch circle of the toothed wheel c to be examined. The bodya is xed on a hollow base Il, and a spindle d on which the workpiece ccan be secured is arranged concentrically with the said body and isattached to a hollow vertical shaft l0 mounted on the bottom of the parta.

Resting on the upper side of the iiXed circular body a is mounted arotatable member e which may conveniently be located by rollers frunning in contact with the periphery of the circular body, and on theupper side of this member e is mounted a slide y. The slide g carriesanother slide h situated adjacent to the workpiece and capable ofsliding at right-angles to the direction of motion of the slide g. Thelatter and the part e are formed with a central gap as i through whichpasses the spindle carrying the workpiece. The slide h carries a feelerwhich is conveniently in the form of a light pivoted lever y' having oneend adapted to bear against one side of the gear tooth to be tested. Theother end of the lever actuates a dial type micrometer l2 carried on h.The lever is kept in contact with the tooth face by the usual spring(not shown) oi the micrometer. The other slide g serves to move theslide h and the feeler j in a radial direction relatively to the axis ofthe workpiece and so enable workplaces of different sizes to beaccommodated in the apparatus, The slide g is adapted to be actuated bya hand wheel l ii secured at the outer end of a shaft it which isjournalled in bearings formed on the rotatable member e, and which is inscrew-threaded engagement with a boss on a bracket El attached to theslide y.

Around a part of the circular portion of the body a is wrapped a thinilexible metal or other strap lc, one end of which is secured to thebody a and the other to any convenient tensioning device such as aiioating rack bar l which engages a pinion m carried on e, the pinionbeing constantly subject to a torque exerted by a weight w or spring(see Figure 2). By reason of this torque and of the co-operating teethon the pinion m and rack bar Z, the latter is caused to maintain thestrap k under tension. The weight w is contained in the hollow base l l,and the torque is exerted on the pinion m by the weight through theagency of a rope or the like passing around pulleys l, 3. A slot i3 isformed in the upper wall of the hollow base to accommodate a shaft lliwinch carries the pinion m and the pulley l. The bar is carried on oneend of the part e by brackets l and is held in position partly bycontact at one side with the body a through the Strap lc and partly bycontact at the other side with rollers n on the brackets ll. When thepart e is rotated relatively to a, it carries the bar l with it and thelatter can also move endwise, but it always occupies a positiontangential to the body a. Also the part e, an extension o of the slide hcarrying the feeler, and the rack bar l (or the strap) are all connectedtogether by a link p.

It will be seen that the link p, which is in the form of a flat bar, isattached at one end to a lug q at one side oi the part e by a pivot r.The extension o is connected to the link by a slider s which is providedwith rollers t bearing on opposite sides of the link and pivotallyattached to o. The rack bar Z is attached to the link p by anotherslider u which is provided with rollers 1J which bear on opposite sidesof the link and is pivoted at 5 on the rack bar. It will be noticed thatthe rollers t of the slider s engage the upper edge of the link p,whilst the rollers 1J of the slider u engage the lower edge.

When the workpiece c has been mounted on the spindle d the slide gcarrying the slide h is moved by means of the hand wheel l5 so as tobring the slider s to a suitable position on the link p. The distancesof the sliders u and s from the pivot r are then in the ratio of thediameter of the body a to the diameter of the base or pitch circle ofthe workpiece, whilst the pivot axis of the slider s` and the contactend of the feeler :i lie in a line which is tangential to the said baseor pitch circle. Also the feeler 7' is brought into contact with oneside of the tooth to be tested as shownv in the drawings. This iseffected by turning the workpiece c, through the agency of a hand wheeli8, about its axis until the tooth side to be tested contacts with thefeeler y'. The hand wheel i3 is secured to the outer end of a shaft i9journalled in the base il and carrying at its other end a bevel wheel i@which, by engaging another bevel wheel 2l secured to the hollow shaft i@permits the motion oi the hand wheel i8 to be transmitted to theworkpiece. The rotatable member c, the ieeler j, the link pi, the rackbar Z and the tensioned strap lc can then all be rotated as a unit aboutthe body a through the desired angular distance, the sliders s and umoving along the link p. Also the slide 7i, moves to a small extent onthe slide g under the control of ie link p. Rotation can be imparted tothe member e by a hand wheel 2?. secured at the outer end or" a shaft 3which is journalled in the iixed body a and which carries a, Worm 263.The worm engages a toothed gear 25 terminating the lower end of a :dange2S depending from the rotatable member e. lt will be evident from thedrawings that when the member c is rotated in a clockwise directionfrom'the position shown, the free end of the strap lc describes theinvolute of the circular portion of the xed body a, that is to say, theinvolute of a circle having a diameter larger than that of the base orpitch circle of the toothed wheel to be examined. The link p and theslide I7, together form what may be termed a reduction link-motionwhereby the involute aforesaid is used for examining the contour of thetoothed wheel. As the free end of the rack bar l is attached to andfollows the movement of the free end of the strap, it also describes thesame involute, and this movement is communicated through the slider u tothe free end of the link p, with the result that similar movement on asmaller scale is imparted to the slider s. As, moreover, the distancesor" the sliders u and s from the pivot r are in the ratio of thediameter of the ixed body a to the diameter of the base or pitchv circleof the toothed wheel being examined, it follows that the eeler itogether with the slide h is caused to describe an involute which isthat of the base or pitch circle of the toothed wheel being examined.During this movement the feeler will traverse the face of the tooth tobe examined. If the tooth is of accurate form, there willbe no relativemovement between the Yfeeler and the slide h which carries it, but if aninaccuracy is present a relative movement will occur and this will beindicated by the micrometer.

The principle underlying the apparatus is already known, and haspreviously been used by me in the testing of gear wheel teeth. yTheapparatus differs, however, in that the body a and workpiece c arefixed, and the feeler is caused to move through the required curved pathdetermined by the unwrapping or wrapping ci the strap lc from or on tothe circular portion of the body. By my invention I am able lto obtainpractical advantages which experience has proved tol be desirable. ThusI am able to provide a robust apparatus which whilst possessing all therequired accuracy is well suited to work-shop requirements. Also, theone iixed body serves for a wide range of Workpieces of differentdiameters.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:-- Y

l. In means for use in examining the contours of gear wheel teeth, thecombination of a xed body having a circular portion, means for securingthe wo-rkpiece co-axially with the said body, a member rotatable aboutthe axis of the iixed body, a slide carried on the rotatable member andmovable relatively to it in a radial direction,

a second slide carried on the first slide and movable at right-angles tothe direction of motion of the nrst slide, a feeler and indicatorcarried on the second slide, a rack bar carried by the rotatable member,a pinion carried by the said member and engaged by the rack bar, aweight, the pinion being constantly acted on by a torque exerted by theweight, a flexible strap arranged around the circular portion Vof thexed body and attached at its ends to the said body and the rack barrespectively, a link pivoted at one side of the rotatab-le member, andmeans for effecting slidable connection between the link and the rackbar and the slide carrying-the feelervand indicator, substantially asdescribed. Y

2. In means for use in examining the contours of gear wheel teeth, thecombination of a xed body having a circular portion with a diameterlarger than those of the workpieces to be examined, means for securingthe workpiece coaxially with the said body, a member rotatable about theaxis of the xedbody, a feeler adapted to move in contact with the gearltooth to be ex-` amined, means slidably mounted on the rotatable memberfor supporting the feeler, a tensionedflexible member embracing a partof the circular portion of the xedl body, means for inter-VV connectingthe rotatable member, the ieeler supporting means and the flexiblemember, the ar. rangement being such that inaccuracy of tooth form willcause the feeler to move relatively to its supporting means uponrotation of the rotatable member, and means forindicating such movementof the eeler, substantially as described.

' JOHNVWILDSMITH SNARRY. Y

